Bag machine

ABSTRACT

The bag machine of the present disclosure is of the type which can produce bags made of various thermoplastic sheet material and can be adapted to make side weld or bottom weld bags. The following description will, however, be confined to the production of side weld bags. A roll of plastic web is mounted on an unwind stand and traverses a folding board constraining the web to fold along its longitudinal median or along a line spaced from and parallel to the longitudinal median in the event it is desired to produce wicketed bags having lip with a pair of holes in which is inserted a U-shape wire called a wicket. Upstream of the folding board a gusseter is provided to produce a fold which permits greater expansion at the bottom of the bag. The folded and gusseted web thence comes under the influence of a reciprocating transversely disposed seal and cutter bar which divides the web, at longitudinally spaced intervals, to produce individual bags. The bags are then transported to a table which is provided with devices for arranging the bags into a stack.

United States Patent Wech [451 May 16, 1972 [54] BAG MACHINE Primary Examiner-Benjamin A. Borchelt Assistant Examiner-J. M. Hanley [72] Inventor. Robert J. Wech, Green Bay, W15. y w. Anderson and C E Tripp [73] Assignee: FMC Corporation [57] ABSTRACT [22] Filed: Sept. 16, 1968 The' bag machine of the present disclosure 15 of the type which PP 760,048 can produce bags made of various thermoplastic sheet material and can be adapted to make side weld or bottom weld bags. 52 us. c1 ..156' s1s,156/251, 156/364 f .z g mm-med 51 1111. C1. ....B32b 31/18, B32b 31/20 Pm e we [58] Field of Search ..156/251,5l5, 353,364; A roll of plastic web is mounted on an unwind stand and 226/142; 83/628; 100/93, 55; 53/180, 182; 93/58.3 traverses a folding board constraining the web to fold along-its longitudinal median or along a line spaced from and parallel to [56] References Cited the longitudinal median in the event it is desired to produce wicketed bags having lip with a pair of holes in which is in- UNITED STATES PATENTS sened a U-shape wire called a wicket. Upstream of the folding board a gusseter is provided to produce a fold which permits 438,528 10/l890 Cox ..226/142 greater expansion at the bottom of the bag. The folded and 2,508,585 5/1950 Stone.... ..l00/93 P UX t d b th d th n f 2 707 985 5/l955 Binnan 156/544 X gusse e we ence comes un er e 1n uence o a 3274043 9 1966 S 6 reclprocatmg transversely d1sposed seal and cutter bar which f 5 6/3 4 x divides the web, at longitudinally spaced intervals, to produce 87 6/1969 wmlams 1 56/353 X individual bagsfThe bags are then transported to a table which 3'494526 2/1970 Calvert et "226/142 x is provided with devices for arranging the bags into a stack. 3,053,723 9/1962 Plach et al. 156/515 X 8 Claims, 24 Drawing Figures O0 410 OZ 31Gb 4 54 o4 354 400 40 0 W r 3: 5348 16 ,342. 34 C 8 ggv Bee 1' 4 I i l h 11/ 5 see 352 ll 424 352 i 1% I 1 a a i ,1 6 41s 44 212 42%94 M\ l a %A fi1 i ll" 296 294 4 1 I 4|Z I06 466 i 290 35'? 85 $22 32 3'24- 4 387 394550 BOG "33 2194 I sec I 22: 2%? 456 4'36 332 [35 h if M VT i Vfl v a new- 2 3 1 z 334 43a 2 442 i 442 540 440 544 430 444 546 5?. 440 430 Patented May 16, 1972 12 Sheets-$heet 1 INVENTOR- ROBERT J. WECH ATTORNEYS Patented l2 Sheets-Sheet 2 IN VENTOR. ROBERT J. WEOH ATTORNEYS ?atented May 16,- 1972 12 Sheets-$heet 5 I NVENTOR. ROBERT J. WECH ATTORNE YS Patented May 16, 1972 3,663,338

12 Sheets-Sheet 4 INVENTOR. ROBERT J. WEGH AT TORNE YS Patented May 16, 1972 1:1 Shea ts-Sheet b m E 0 J E m NE 18 o R ATTORNEYS Patented May 16, 1972 12 Sheets-Sheet G k I I! 1 9w mmw 6. A55 TEN DEN 91w ,5 55

INVENTOR. ROBERT J. WEGH nNiN ATTORNEYS Patented May 16, 1972 12 Sheets-Sheet W INVENTOR. ROBERT J. WECH ATTORNEYS Patented May 16, 1972 3,663,338

12 Sheets-Sheet 8 INVENTOR. ROBERT J. WECH BYJMW AT TORNE YS Patented May 16, 1972 3,663,338

12 Sheets-Sheet 11 on 9 4M N o INVENTOR. F! q 5 ROBERT J. WEOH m 0 w@@\ g 8 i N 85% V m 6% P ATTORNEYS Patented May 16, 1972 l2 Sheets-Sheet l2 NNv Nmm

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@EV/T ATTORNEYS BAG MACHINE BACKGROUND OF THE INVENTION In order to attain a production rate of 200 or more quality thermoplastic bags per minute it is essential to design the bag making machine with features that provide: a) positive control of the film during its unwinding from the parent roll; b) maintenance of a fixed positional relationship between the parent roll supporting stand and the infeed frame of the baging machine; c) when desired, a gusseting mechanism which provides a minimum drag to the film while insuring a gusset of constant depth; d) web draw rolls whose nip pressure is evenly distributed and has the ability to apply a differential nip pressure from one end of the rolls to the other; e) incorporating mechanisms which will release the nip pressure in the event film movement is stopped to prevent the creation of flat spots on the film; f) a seal bar which will maintain a uniform evenly distributed temperature throughout its length and one that is shielded to prevent heat loss to the film; g) a seal bar drive arranged for a manual or automatic lift when desired or when web feeding is interrupted for any reason; h) mechanisms to vary the length of the bag being produced while the machine is operating to correct or change the size of the bags accurately under operating conditions with no down time and; i) a bag transporting conveyor, which conventionally runs at higher speed than the film, including an easily adjustable positive control arrangement whereby adjustments can be made under operating conditions to insure that the trailing end of the bag is engaged by a conventional bag slow down mechanism to stack the bags so that their margins are in registration.

SUMMARY OF THE INVENTION Therefore in accordance with one feature of the present invention a web or film unwind stand is provided with the ability to maintain a fixed relationship with the infeed frame of the bag machine for purposes of insuring accurate alignment of the stand with the bag machine. Such acondition is necessary to insure proper tracking of the film through the bag machine and to prevent the creation of wrinkles in the web. In making side weld bags the unwind stand is supplied with a roll of film whose width determines the depth of the bag to be produced. It is conventional practice to train the web over a V-shaped folding board, hereinafter sometimes referred to as a V-board or folding board, which constrains the web to fold upon itself before being received by draw rolls mounted on the infeed frame of the bag machine. As will be made evident the unwind stand must be positioned so that the axis of the parent roll of stock is exactly or substantially exactly parallel to the longitudinal median of the bag machine. Stated another way the longitudinal median of the film must unwind so that it defines an angle of 90 to the path the folded film takes through the bag machine. In achieving this objective the present invention provides a very rigid locating frame connected to the infeed frame of the bag machine. The locating frame is provided with a member establishing a guideway or rail which is engaged by roller guides carried by the V-board and the base frame of the unwind stand. Such construction allows movement of the unwind stand normal to the longitudinal median of the bag machine and thus insures that the above'described relationship is maintained irrespective of the width of the film or whether the machine is used as a double lane machine.

Another equally important feature of the present invention is the provision of a gusseting mechanism which makes a gusset of constant depth, is rapidly adjustable to change the depth of the gusset and is movable transversely in the event it is desired to change the path of the film relative to the longitudinal median of the bag machine. To achieve such flexibility it is preferable if not essential that the gusseter be mounted at a place where the speed of the web is substantially constant so as to obviate the problems of uneven gusset depth due to film bounce. To fulfill this condition the gusseter of the present invention is mounted between the folding board and the infeed frame of the bag machine. The construction of the gusseting attachment is designed so that an operator can rapidly and easily adjust the gusseter to produce gussets of a wide range of depth and it also has the ability to reduce, to an absolute minimum, drag imposed on the film thereby reducing the nip pressure of the web feeding rolls. The gusseter is also designed to facilitate threading of a new roll of film into the machine. This is desirably accomplished by moving the gusset forming wheel out of contact with the film.

In accordance with a further feature of the present invention the film feeding draw rolls, which assist in feeding the film from the parent roll, are arranged so that the nip pressure applied to the film can be easily varied and if desired a differential nip pressure can be produced if desired. The preferred construction giving rise to this result comprises pneumatic cylinders or jacks arranged to apply a force to each end of the upper draw roll and the pressure to each cylinder can be equal, unequal or interrupted thereby removing all nip pressure. Removal of the nip pressure is usually desirable when the bag machine is stopped and this can be accomplished manually or automatically, as desired, thus preventing the creation of flat spots on the film.

Further in accordance with the present invention an improved seal bar and drive is provided which produces, respectively, a uniform temperature throughout its length without distortion or excessive conductive heat losses and a drive which is arranged so that the seal bar can be manually or automatically lifted from its operative position as desired. Automatic lifting of the seal bar is particularly advantageous when the bag machine is programmed for a jogging mode or when the machine is stopped for any reason. The seal bar drive is also provided with the ability for partial or full lift in such situations where the machine is set up for skip-draw utilized where extra wide bags are desired. It is also automatically lifted when the bag machine is set to interrupt its operation after a predetermined number of bags have been produced.

The above features improve the flexibility of the machine and the quality of bags made since continued reciprocation and contact of the seal bar at one of the side welds distorts the film and destroys the bag containing the seal repeatedly struck by the seal bar. Moreover lifting of the seal bar when the machine is stopped prevents damage to the film arising from overheating when web development is interrupted,

A further and equally important feature of this invention is the provision of mechanisms to vary the length of a bag being produced while the machine is operating so that the desired size of bag can be accurately determined under operating conditions without interruption of web development. While this feature is conventional in presently available commercial bag machines, this invention discloses an improvement wherein more reliable and trouble free operation results. The present design fulfills this goal by incorporating rigid thermoplastic blocks which are selectively engageable with a moving metal member and thereby effectively absorbs the impact without damage to the operating parts. Further by this arrangement metal chips are not generated which could interfere with the operation of the bag machine.

Still another feature of this invention is the provision of means for controlling the speed of the bag transporting conveyor to effect separation of the bags downstream of the seal bar so as to prevent contact between the seals of adjacent bags and thus avoid possible sticking. With the increase in velocity problems are encountered in constraining the bags to produce neat stacks since the stiffness of the film is not sufficient to overcome an abrupt stop against fences mounted on the stacking table. The bag machine of this invention makes use, therefor, of a conventional bag slow down device which momentarily grasps the trailing end of the bag prior to its encountering the bag stacking fences. To insure grasping of the bag at its trailing end the present invention provides a direct current drive motor for the bag transporting conveyor which can be accurately adjusted to synchronize its speed with the slow down device.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B, when viewed together along the break line R show the bag machine of the present invention in Iongitudinal section wherein the path of the web is shown by a broken line and the direction of web feed is indicated by arrows applied thereto,

FIGS. 2A and 2B, considered together along the break line S, illustrates the bag machine in plan view,

FIG. 3 is a partial perspective of the unwind stand on reduced scale showing its connection to the infeed frame of the bag machine,

FIG. 4 is a section taken substantially along the line 4--4 of FIG. 2A showing a front elevation of the unwind stand on reduced scale, and of a simplified character, further illustrating the unwind stand guiding system,

FIG. 5 is a perspective of the gusseting attachment made in accordance with the present invention,

FIG. 6 is a plan view of the gusseting attachment,

FIG. 7 is a front elevation of the gusseting attachment taken substantially along the line 77 of FIG. 6,

FIG. 8 is a section taken substantially along the line 88 of FIG. 7,

FIG. 9 is another section taken substantially along the line 99 of FIG. 7,

FIG. 10 is a partial section, on enlarged scale, taken along the line l0--I0 ofFIG. 6,

FIG. I1 is a perspective, on an enlarged scale and with parts broken away, showing the construction of the mechanism for changing the bag length changing device,

FIG. 12 is an enlarged fragmentary portion, partially in section, showing the construction of the mechanism for changing the nip pressure of the draw rolls,

FIG. 13 is a section taken substantially along the line 13- 13 of FIG. 1B illustrating the seal bar drive and the bag length changing mechanism,

FIG. 14 is a fragmentary portion, on enlarged scale, taken along the line 14-l4 of FIG. 2B, showing the relationship of the seal bar, the seal roll and the draw rolls,

FIG. 15 is a section of FIG. 14, on a reduced scale, taken substantially along the line l5l5,

FIG. 16 is a simplified diagrammatic perspective of the drive train of the bag machine,

FIG. 17 is a fragmentary side elevation of the bag length changing device on reduced scale,

FIG. 18 is a schematic of the circuit for regulating the speed of the index conveyor of the bag machine,

FIG. 19 is a fragmentary perspective of the top portion of the seal bar support showing a graduated dial for adjusting the penetration of the seal bar,

F I6. 20 is an enlarged scale fragmentary partially in section, of the upper portion of the seal bar drive when it is in its operative position.

FIG. 21 is similar to FIG. 20 with the exception that the seal bar is shown in its lifted non operative position and,

FIG. 22 is an enlarged plan of the seal bar adjustment indicator.

DESCRIPTION OF THE PREFERRED EMBODIMENT GENERAL ARRANGEMENT With reference to FIGS. 1A, 1B, 2A and 28 it will be noted that the bag machine of the present invention is generally indicated by the numeral 20 and it comprises an unwind stand 22 (FIG. 2A) rotatably supporting core shafts 24 which in turn support film rolls 26. The web, designated by the letter W, unwound from the roll 26 is folded along a line parallel to its ends by a folding board or a V-board 28. When so called even edged bags are made the fold line is located at the longitudinal median of the web while the fold line for lipped bags is spaced from and parallel to the longitudinal median. FIG. 2A shows the V-board set up for producing lipped bags since the left hand margin of the web, identified by L. I'I., is laterally spaced from the right hand margin R. H. downstream from the V- board 28. The web then comes under the influence of a gusseting mechanism 30 which forms an inwardly directed fold on that portion of the web which defines the bottom of the completed bag. The fold is shown by a dotted line in FIG. 2A and is identified by numeral 32.

Referring to FIG. 1A it will be seen that the gusseting mechanism 30 is mounted on support arms 34 pivotally connected to a transverse rod 36 mounted to and extending between laterally spaced infeed frame members 38. Rotatably supported on the transverse rod 36 is a roller 40 which directs the web between a first set of infeed rolls of 42 connected to conventional nip pressure regulating means 43. The web is thence trained about a plurality of idler rollers 44, mounted on dancer arms 46, and rollers 48 extending between and rotatably mounted on the infeed frame members 38. The length of web accumulated in the path defined by the rollers 44 and 48 serves to provide a temporary supply which automatically increases or decreases in response to transient values of web tension. This arrangement tends to produce a constant value of web tension.

The bag machine frame comprises a base plate 50 having mounted thereon transversely spaced upwardly projecting side frame members 52 located substantially at the mid portion of the machine. At the discharge end, outfeed frame members 54 are also mounted on the base plate 50 and served to support bag discharge control devices explained in detail hereinafter.

Referring again to FIG. IA it will be observed that between the infeed frame members 38 and the mid-frame members 52 a horizontal accessory platform 56 is connected therebetween and it serves to support hole punching assemblies 58 mounted on a base plate 60. As shown in FIG. 2B the base plate 60 is mounted on a rectangular frame 62 and is transversely adjustable on this frame. It is held in a selected transverse position by a lock screw 64. Longitudinal adjustment of the rectangular frame 62 carrying the hole punch assemblies 58 is accomplished by racks 66 and pinions 68. As shown diagrammatically in FIG. 2B the racks 66 are fixed to the inner surfaces of the side rails 56 while the pinions 68 are keyed to a transversely extending shaft 70 rotatably mounted in the rectangular frame 62. On one end of the shaft 70 a knob 72 is keyed for rotating the shaft 70 and consequently adjusting the longitudinal position of the hole punching assemblies 58.

Upstream of the hole punching assemblies 58 an electronic web registration device 72 commonly referred to as a scanner, is likewise mounted for longitudinal and transverse adjustment. Longitudinal adjustment is accomplished by pinions 74 (FIG. 1A) in mesh with the racks 66. The pinions 74 are mounted on a transverse shaft 76 rotatably carried in generally L-shaped in frames 78. On the upright legs of the L frames 78 a transverse bar 79 is secured. Slidably mounted on the bar 79 is the scanner 72 which can be locked in any transverse position by a lock screw 80. On the horizontal leg of the L frame 78 a transverse bar 82 is mounted and it will be observed, by inspection of FIG. 1A, that its upper surface is in substantially the same plane as the web line. In order to insure repeated response of the scanner the upper surface of the transverse bar 82 is white in color so as to provide good contrast for detection of the printed registration mark. As is conventional the scanner is electrically connected to the control circuit of the bag machine to deenergize the clutch and simultaneously energize the brake thereby arresting the movement of the web for a sufficient period of time to allow the transverse seal bar to operate and thereby make the side weld for two longitudinally adjacent bags. After the seal bar completes its function the control circuit is then conditioned to release the brake and engage the clutch commencing web movement.

As shown in FIG. 1B upstream of the scanner the web passes between intermittently operating draw rolls 84 associated with upper and lower sets of the stripper fingers 86 and 88, respectively, detachably mounted on transverse bars 90 and 91. The draw rolls are connected, as hereinafter will be more particularly described, with means, generally indicated by the numeral 92, for controlling the nip pressure the draw rolls exert on the film and for removing the nip pressure when required, either selectively or automatically.

To resist the deflection of the draw rolls, particularly at their mid portion and thereby insure an even value of nip pressure along the length of the draw rolls, a back-up roll 94, in rolling contact with the lower draw roll, is provided. The backup roll 94 is rotatably mounted in a yoke 96 having a link extension 98 which forms one link of a parallel linkage mechanism 100. The vertical position of the back-up roll 94 and accordingly the back-up force it will apply to the draw rolls 84 can be selected by adjusting a screw jack 102.

Immediately upstream of the draw rolls there is provided a vertically reciprocating sealing mechanism 104, cooperating with an intermittently rotating seal roll 106 for making the transverse seals in the folded web These seals constitute the lateral margins of the bags. The seal mechanism is reciprocated by a pair of cams 108 (one of which is shown in FIG. 1B) keyed to a shaft 110. The specific construction of this arrangement will be more fully described in connection with the apparatus shown in FIG 13.

After the web passes the seal mechanism individual bags are at that time produced and they are received by a continuously operating belt conveyor 112. The index conveyor comprises a series of transversely spaced and aligned upper and lower sets of belts, 114 and 116 respectively, moving in a direction indicated by the arrows in FIG. 18. Those reaches of the belts which are traveling from left to right, as viewed in FIG. 1B, are in contact for the purpose of gripping the bags discharged from the sealing mechanism and transporting them to a stacking table 118 provided with adjustable stop plates 120 for collecting the bags in a stack.

The upper belts 114 of the index conveyor 112 pass around an idler shaft 122 rotatably supported on linkages 124 mounting a cam follower roller 126 which is held in engagement with a cam 128 by a spring 130. As shown in FIG. 1B the cam 128 is mounted on a shaft 132 and during operation the linkages 124 are oscillated raising and lowering the idler shaft 122 which serves the purpose ofaccommodating any over travel of the bags as they issue from the sealing and cutting mechanism 104 and thus prevent wrinkling ofthe bag.

Before the bags are discharged to the stacking table 118 they come under the influence of conventional corregating rollers 134 which serve to stiffen the bag in the direction of movement so as to prevent distortion thereofas it is ejected to the stacking table 118. Before being discharged to the stacking table the trailing end of the bag is momentarily gripped by a slow down mechanism 136 of known construc- {1011.

In order to synchronize the speed of the belt conveyor so that bags discharged therefrom are momentarily gripped at or adjacent their trailing edge, an electrically adjustable direct current drive arrangement 138 is provided. While the details of construction of the direct current drive will be explained in greater detail in connection with showings of FIGS. 16 and 18, preliminarily it is to be observed that FIG. 16 shows a DC motor 140 driving a belt 141 trained about a pulley 142 which is keyed to a shaft 143. The shaft 143 has a pulley 144 at its opposite end which drives a belt 145 trained about a pulley 146 mounted on a shaft 147 being the input shaft to the belt conveyor drive. For purposes of maintaining the proper ten sion on the belt 142, a tightner pulley 148 (FIG. 1B) is provided and it is carried by a stub shaft 150 mounted on an adjustable arm 152.

UNWIND STAND FIGS. 2A, 3 and 4 show the novel unwind stand of the present invention which, as mentioned above, is structurally unified with the bag machine to insure proper tracking of the web regardless of its position along a line which is normal to the longitudinal median of the bag machine. Referring to FIGS. 3 and 4 it will be observed that the unwind stand comprises a platform 154, of generally rectangular configuration, rotatably mounting wheels 156 which allow the platform to be moved as desired. The platform has mounted on its upper surface a frame structure 157 having opposed side plates 158 interconnected by parallel, laterally extending, bars 160. Rollers 162, running in tracks 164, mount the frame structure 157 for lateral movement relative to the platform 154. Such movement is required to maintain one edge of the film fixed with respect to a reference point so that bags of consistent dimensions are produced. Such lateral movement on the frame -by rails 184 and structure 157 is effected by a conventional edge guide, preferably of the pneumatic hydraulic type, which controls the extension and retraction of a hydraulic cylinder 166 connected, as shown in FIG. 3, to the platform 154 by a bracket 168 and to one .of the side plates 158 by a clevis connection 170. The hydraulic cylinder is extended or retracted by the edge guide sensing control (not shown) so as to keep one margin of the film located in a predetermined position with respect to the platform 154.

The unwind stand 22 is joined to the bag machine so that it is allowed to move in a direction transverse to the longitudinal median of the bag machine and in a direction normal thereto thus serving to position the folded web transversely to the bag machine. This is particularly important where the bag machine is associated with two unwind stands which feed folded roll stock to the bag machine, which as a result, produces two bags each time the seal and cutter bar is reciprocated. To insure movement of the unwind stand in the mentioned normal direction, a guide rail 172 is rigidly connected to the infeed frame members 38 by structural members 174. On the platform there is rigidly connected a slotted block 176 rotatably carrying rollers 178 which are in rolling engagement with the opposed vertical surfaces of the guide rail 172. An A frame 180 connected to the platform 154 carries a roller 182 in rolling engagement with the upper surface of the guide rail 172. As shown on FIG. 2A the guide rail 172 extends a sufficient distance laterally of the bag machine to allow positioning of the unwind stand at any desired operating position.

While it is not shown, the platform 154 can be rolled by a crank mechanism to position the unwind stand as desired. Regardless of the transverse location of the unwind stand it will always maintain its normal relationship with the longitudinal axis of the bag machine by virtue of the guide rail 172 and the rollers 178 and 182 which constrain the unwind stand to maintain its desired attitude.

GUSSETING MECHANISM The gusseting mechanism 30, generally referred to in the above described general arrangement, is shown in greater detail in FIGS. 5 through 10. Referring first to FIG. 5, which shows an enlarged perspective of this mechanism, it will be seen that the gusseting mechanism is supported on the arms 34 186 rotatably carrying a shaft 188 having keyed thereon pinions 190 and 192. The pinions are in mesh with racks 194, 196 fixed to the inner vertical surfaces of the support arms 34. The pinions 190, 192 are held in place on the shaft 188 by collars 198. The shaft 188 has a threaded extension beyond the rail 186 and has threadedly mounted thereon a jam nut 200, serving to lock the shaft against rotation, and a hand wheel 202 secured to the shaft 188 for effecting rotation thereof to thereby cause longitudinal translation of the gusseter mechanism 30 whenever the shaft 188 is rotated.

Rigidly attached to the upper surface of the rails 184 and 186 is a support plate 204 provided with a slot 206. The support plate 204 has attached thereto a mounting bracket generally indicated by the numeral 208 for rotatably supporting a gus'seter wheel 210 which, when in its operative position is located between stationary gusseter plates 212 and 214, the upper and lower plate respectively These plates are rigidly fastened to a laterally adjustable support bar 216 overlying and spaced from a lower support bar 218 by a spacer block 220.

The gusseter mounting bracket 208 is shown in side elevation in FIG. 9 and reference to this Figure will show that the bracket comprises an elongate rectangular bar 222 secured to the support bar 218 by bolt 224 having slidably fitted thereon a bushing 226 which is received in the slot 206 and is dimensioned to provide a sliding fit. As will be evident by inspection of FIGS. and 6 it will be seen that the bar 222 extends sub stantially normal to the support plate 204 and adjacent its outboard end it is tapped to threadedly receive a pivot bolt 228 passing through a boss 230 of an arm 232 rotatably mounting the gusseter wheel 210 on a small flat-head screw 234.

Also projecting from the boss 230 is a lug 236 carrying a pin 238 having a spring biased ball 240 mounted in a retaining sleeve 242. As shown in FIG. 6 the rectangular bar 222 has a spherically shaped depression 244 located to receive the spring biased ball 240 when the gusseting wheel 210 is moved to the phantom outlined position shown in FIG. 6. This holds the gusseting wheel in that position and its main purpose is to facilitate threading of the film through the gusseter. Prior to repositioning the wheel for gusseting, hand folding of that portion of the film adjacent the plates 212 and 214 can be done before the wheel 210 is located between the gusseting plates 212 and 214.

The gusset forming members, that is the plates 212, 214, and the gusseting wheel 210, are arranged so that they can be located transversely relative to the longitudinal median of the bag machine. Such an adjustment is required when it is desired to produce bags of different length. For example if the film roll on the unwind stand is 24 inches wide the maximum length of a non-gusseted bag would be half that length or 12 inches; while a gusseted bag made from the same film roll would be reduced in length by the amount used for the gusset. In the event film of greater width is used in order to produce gusseted bags of greater length it would be necessary to move the gusseting wheels 210 and the gusseting plates 212 and 214 to the right, as viewed in FIG. 5. For this purpose a clamping arrangement 246 is provided. With particular reference to FIG. 5 and 8 it will be observed that the clamp 246 comprises a generally U-shaped base member 248 rigidly attached to the support plate 204 by fasteners 250. The base member 248 is formed so that the support bar 218 slidably fits in the generally rectangular space defined by the base member 248 and the plate 204 (FIG. 8). Disposed above the base member 248 there is a clamping bar 252 having a clearance hole adjacent one end through which is disposed a bolt 254 threaded into the base member 248. On the other end of the bar another clearance hole is provided having disposed therein a stud 256 also threaded into the base member 248 and provided with a knob 257. At the intermediate portion of the clamping bar 252 a set screw 258 is threaded therein, bearing on the upper surface of the bar 216, and is in forceable contact therewith when the stud 256 is tightened. This of course locks the bars 216 and 218 in place and accordingly maintains the lateral position of the gusseting wheel 210 and the gusseting plates 212 and 214 since they are mounted, respectively, to the bar 218 and the bar 216. In view of the above it will be apparent that when it is desired to change the lateral position of the gusseting wheel 210 and the plates 212 and 214 all that is necessary is to loosen the stud 256 sufficient to remove the force supplied by the set screw 258 to the bar 216. The desired position of the gusseting mechanism can then be achieved manually by pushing or pulling the interconnected bars 216 and 218.

In order to accommodate the gusseter mechanism 30 to the machining characteristics of the film and to prevent damage to the film in the event portions of the film exhibit more or less resistance to formation, the gusseter wheel 210 is held in its operative position between the plates 212 and 214 by a spring 260. As shown on FIG. 9 one end of the spring 260 is attached to a hook 262 having a threaded stem threaded into the arm 232. The hook 262 is held against rotation by a jam nut 264.

The other end of the spring 260 is attached to a bead-chain 266 which extends beyond a catch 268 mounted on a bracket 270. As will be observed by reference to FIG. 8 the catch 268 is formed with two upwardly extending fingers which fit between adjacent beads of the chain 266. On the remaining end of the chain 266 a ring 272 is secured which serves to facilitate grasping of the chain and consequent tensioning of the spring 260 to the degree required by the forming characteristics of the film. When a desired. degree of tension is achieved usually determined by observing film formation while the machine is running, the chain is inserted between the upwardly extending pins of the catch 268. Accordingly it will i be seen that by utilizing the spring 260 for urging the gusseter wheel 210 between the plates 212 and 214 the gusseter has the ability to give in the event increased resistance is encountered consequently preventing damage to the film.

Another and further novel feature of the gusseter mechanism pertains to the general configuration of the gusseter plates 212 and 214. As will be observed these plates are generally rectangular in configuration and are made arcuate at the intersection of the margins. As is known by those skilled in the art, regardless of their design, gusseting attachments wear rather rapidly even though surface preparations such as Teflon are applied to those portions of the gusset forming members which come in contact with the film. While the gusseting mechanism of the present invention reduces the wear to an absolute minimum, particularly on the gusseting wheel 210 since it is mounted for rotation thereby obviating or minimizing relative velocity between the gusseting wheel 210 and the film, the gusseting plates 212 and 214 do encounter an appreciable amount of friction and thus are subject to wear. As shown in FIG. 10 the film encountering edges of the gusseting plates 212 and 214 are identified as 2120 and 214a respectively. The plates 212 and 214 are provided with an auxiliary set of mounting holes, collectively identified by the numeral 278 (see FIG. 6) which correspond to the spacing of the mounting holes containing the screws 280. When the edges 212a and 214a are worn to the extent that the gusseting function is impaired the plates 212 and 214 are removed and are repositioned on the support bar 216 locating edges 2121: and 214b to make contact with the film and thus cooperate with the gusseting wheel 210 tov form gussets.

While the above arrangement of reversing the plates to use opposed margins of the plates 212 and 214 to extend their useful life, it is within the scope of this invention to form the plates so that all four edges may be used.

DEVELOPMENT CHANGE DEVICE In accordance with a further feature of the present invention an improved development change mechanism is provided which is more reliable in operation due to the fact that metal to metal contact between a rotating member and a stationary member is obviated. More particularly the bag machine of the present invention comprises a mechanism'for selectively varying the throw of a crank which is connected to a shaft to thereby control the amount of shaft rotation. Variation of the crank throw is accomplished while the bag machine is in operation thus allowing the operator to visually determine when the desired bag width is produced.

In describing this feature of the present invention reference will be made to FIGS. 11, 13, 16 and 17. Referring first to FIG. 17, which shows a fragmentary portion of the side frame member 52, it will be seen that the change device comprises a ledge 286 rigidly attached to the side frame member 52 and it has extending therethrough a shaft 288 mounted for rotation in longitudinally spaced ears 290 of a plate 292 that is bolted to the side frame member 52. On the upper end of the shaft there is attached a lever 294, provided with a knob 296, for rotating the shaft 288. FIGS. 11 and 13 show this construction in greater detail. At the lower end of the shaft 288 there is secured a small rectangular fiat plate 298 and said plate has rigidly attached thereto spaced blocks 300 and 302 preferably made of polyurethane although any suitable plastic material such as nylon can be utilized. The blocks 300 and 302 are tangent to and straddle the orbit of a star wheel 306 keyed, or otherwise suitably attached, to a screw 308. As shown in FIG. 1 1 a block 310 is slidably mounted in a guide way 312 formed with a conventional dove tail slot. In FIG. 17 it will be observed that the screw 308 is fixed against axial movement relative to the guideway 312 by having pinned thereon a collar 314 bearing against an end stop or plate 316.

Integral with the slider block a projecting stub shaft or crank pin 320 is provided, on which is rotatably mounted, one end of a crank 322 while the other end of the crank is rotatably mounted on a pin 324 (FIG. 16) integral with a sector gear 326 mounted for oscillation on a trunion 328 which is in turn secured to the side frame member 52.

As shown in FIG. 13, the guideway 312 is bolted to a support plate or platform 330 that is bolted to a coupling 332 having a reduced diameter portion located in a bearing 334 carried by one of the side frame members 52. The coupling 332 is keyed to the shaft 110 and accordingly rotates therewith.

As shown in FIG. 17 a scale 336, calibrated to indicate bag width, is secured to the guideway 312 and on the slide 310 a pointer 338 is mounted and it indicates the bag width setting. As will be apparent when the axis of the crank pin 320 defines an extension of the axis of shaft 1 the crank 322 is not oscillated thus the sector gear 326 will remain stationary. It will be evident therefore that the distance between the axis of the crank pin 320 and the axis of the shaft 110 will determine the angle of oscillation of the sector gear 326.

Operation of the development change device will be explained in connection with the showing of FIG. 11. The full line position of the lever 294 and the rectangular plate 298, connected thereto by virtue of the shaft 288, is the position assumed which will allow passage of the star wheel between the blocks 300 and 302 without coming in contact with the star wheel 306 and thus rotation of the screw 308 does not take place. When it is desired to increase the bag width, and accordingly increase the distance between the axis of the crank pin 320 and the axis of the shaft 1 10, the lever 294 is manually pivoted to the phantom outline position which concurrently turns the plate 298 thereby orienting the block 302 to engage and turn the star wheel 306 as it moves past the block 302. Rotation of the star wheel 306 rotates the screw 308 causing downward movement of the slider block 310 thereby increasing the distance between the axis of the pin 320 and the axis of the shaft 1 10. It should be apparent that if the lever 294 is held in this position the slider block 310 will be incrementally lowered each time the star wheel 306 engages the block 302. Conversely decreases in the distance between the axis of the pin 320 and the axis of the shaft 110 is accomplished by moving the lever 294 in the opposite direction causing the block 300 to engage the star wheel 306 thus rotating the screw 308 in the opposite direction which causes raising of the slider block 310.

While the general organization of the above described development change device is known in the art the present invention gives rise to smoother and more trouble free operation by virtue of making the blocks 300 and 302 of polyurethane. In prior art devices the star wheel is indexed by coming in contact with another metal part thus giving rise to detrimental shock loads and the production of metal chips which more than likely infiltrate the bearing surfaces of the machine and cause interruptions of production and significant increases in maintenance cost.

SEAL BAR AND DRIVE In accordance with another feature of the present invention a new and improved seal bar mounting and drive is provided. In present commercially available bag machines it is usual to continue reciprocation of the seal bar whenever web development is interrupted for any reason. Continued reciprocation of the seal bar causes damage to the seal roll. Further, such continued reciprocation of the seal bar destroys the sealed portion of the web which is arrested under the seal bar since repeated contact therewith by the seal bar causes destruction of the film due to its repeated exposure to heat and will in some cases burn back the film rendering the resulting bag useless.

This feature of the present invention will be described with reference to FIGS. 13 and 14. As shown in FIG. 13, a seal bar 340 extends downwardly from and is mounted to a beam 342 by thin V-shaped metal clips 344. With reference to FIG. 14 it will be observed that the beam 342 comprises two elongate rectangular beams 346 connected at either end by spacer blocks 348 formed with short trunions 350 which are received in mounting blocks 352 and are captively secured therein by bearing caps 354. When in its operative position the seal bar 340 is directly above the seal roll 106 and its knife edge 355 makes contact with the seal roll.

The seal bar 340 is maintained in this position by a latch arrangement 356. The latch 356 is connected to one of the elongate bars 346 by a spacer block 358 and a bar 360 which is joined to the spacer block 358 either by welding or bolting as desired. A rod 362, slidably mounted in a hollow handle 364 and extending through an aligned hole in the bar 360, has a knob 366 mounted thereon and is biased to the left, as viewed in FIG. 14, by a spring 368 so that the left end of the rod is received and maintained in bores 370 formed in a plate 372 shaped to define a circular segment. With the pin 362 seated in the bore 370a the seal bar 340 is disposed in its operative position. To render the seal bar inoperative, that is to say it will not encounter or make contact with the film when the seal bar drive is operating, it is merely necessary to retract the rod 362 from the hole 370a by exerting a force on the knob 366 and rotating the latch assembly 356 sufiiciently to align the rod 362 with the hole 37%. Since one of the seal bar mounting beams 346 is rigidly attached to the spacer block 358 and the bar 360, it should be apparent that the seal bar 340 is rotated about the axis of the short trunions 350.

Actuation of the seal bar 340 toward and away from the seal roll 106 is accomplished by a novel drive mechanism generally designated by the numeral 374. This mechanism enables the seal bar to be raised, manually or automatically, as desired, with automatic lifting being of particular benefit for skip draw, a predetermined count, or when the machine is stopped. Moreover the push rod design, explained in detail hereinafter, obviates backlash problems which are attendant with seal bar drives of the prior art. The cam design of the drive mechanism is designed to facilitate adjustment of the dwell to the characteristics of all known films used to produce bags.

Referring now to FIG. 13 it will be observed that the cams 108 are keyed to the shaft 110 and are in rolling engagement with cam follower rollers 376 rotatably mounted on pins 378 carried by brackets 380. The brackets 380 are rigidly attached to the lower end of push rods 382 and are formed with a laterally extending lug 384 mounting an upwardly extending guide pin 386 extending through a spring 387. The guide pins are slidably received in retaining caps 388 which are rigidly attached to a stationary frame member 390.

The frame members 390 carry tubular sleeves 392 with bearings 394 mounted at each end and interiorly thereof through which extend the push rods 382. At the upper end of each push rod 382 a nylon disc 396 (FIGS. 20 and 21) is attached and it makes contact with an enlarged disc shaped head 398 of a bolt 400 which is threaded through a cap 402 secured to the upper end of the mounting blocks 352. As shown the stem of the bolt 400 projects above the cap 402 and it has threaded thereon a jam nut 404 which locks the bolt 400 in place. The bolt 400, as will be explained in greater detail hereinafter, can be adjusted relative to the cap 402 when the jam nut 404 is loosened by merely inserting a screw driver in the milled slot 406 and its adjusted position can be determined by aligning an index mark 408 with graduations on an annular scale 410 suitably affixed to the upper surface of the caps 402.

Adjustment of the bolt 400 moves the mounting blocks 352 and of course the seal bar 340, since it is connected to the mounting blocks by the trunions 350, relative to the seal roll 106 which is rotatably supported by bearings 412 to the stationary frame members 390. By this adjustment the penetration force of the seal bar against the seal roll may therefore be accurately and easily adjusted and the adjusted position can be easily determined by observing the setting of the screws 400.

Adjacent the upper surface of the frame members 390 and rigidly fixed to the push rods 382 are brackets 414 mounting downwardly extending pneumatic cylinders 416. The cylinders 416 have their rod ends threaded into ears 418 which are integral with the mounting blocks 352. Conduits 420 and conduits 422 are respectively connected to the rod end and the head end of the cylinders 416, and are controlled by conventional electrically operated valves (not shown) operated by the control circuit of the bag machine. As usual, the valves operate to admit pressure fluid, from any suitable source, to the rod end or head end of the cylinders 416.

When the head ends of the cylinders 416 are pressurized extending the rods, the mounting blocks 352 and the seal bar 340, are raised upwardly relative to the push rods 382. To guide the mounting blocks 352 in such circumstances ball bushings 424 are provided slidably engageable with a sleeve 426, secured to the mounting blocks 352, and the push rods 382.

As mentioned previously the bag machine of the present invention is provided with means to effect semiautomatic lifting of the seal bar when the machine is being set up and the control circuit is conditioned for jogging. Further, whenever the bag machine is stopped automatic lifting of the seal bar takes place while on starting automatic drop is effected. Automatic lifting also takes place after a predetermined number of bags have been made. Machine operation is interrupted for a period necessary to permit the operator to remove a stack of bags from the table 118. Thereafter operation is' resumed upon automatic lowering of the seal bar.

Referring now to FIGS. 20 and 21 which show, respectively, the seal bar 340 in contact with the seal roll 106 and the raised position of the seal bar. As mentioned previously, the draw rolls 84 are intermittently rotated feeding the folded and gusseted web to project between the seal roll 106 and the seal bar 340. During that increment of time the web movement is arrested the seal bar moves downwardly, by virtue of the cams 108, to produce a side weld. As will be explained, the increment of time that the seal bar 340 remains in contact with the seal roll is determined by the amount of cam dwell which can be varied to suit the characteristics of the film or web. During normal operation of the bag machine the seal bar 340 is raised approximately five-eighths of an inch above the seal roll 106 during such times that the web is fed by the draw rolls 84. The amplitude of seal bar reciprocation during normal operating conditions is determined by the cams 108. Under such conditions the cylinders 416 are maintained in their retracted position by supplying fluid through the conduit 420 which, as will be readily observed by inspection of FIG. 20, maintains the head 398 of the bolt 400 in forcible contact with the nylon disc 396. The cylinders 416 may therefore be thought of as fluid clamps and since they are mounted on brackets 414 which are in turn rigidly attached to the push rods 382 they reciprocate with the seal bar during normal operation.

FIG. 21 shows the seal bar in its lifted nonoperative position. It will be observed that it assumes this position by virtue of the extension of the cylinders 416 which, as is conventional, is caused by operation of a control valve that exhausts the fluid from the rod end by conduit 420 and admits pressure fluid to the head end by conduit 422. This obviously causes extension of the cylinder rod 428 which moves the mounting blocks 352 upwardly relative to the push rod 382. As explained above, automatic full or partial lift takes place when the machine is shut-down, when a predetermined number of bags have been made, or when skip draw operation is desired.

The seal bar drive as shown in FIG. 13 is also provided with a cam design which can be adjusted to provide variations in dwell time so that the time in which the seal bar is in contact with the thermoplastic film can be adjusted to the particular characteristics of the film. As shown in FIG. 13 each of the cams 108 comprise a stationary cam portion 430 rigidly attached to an adapter plate 432 by means of bolts 434. The plate 432 is secured to the cam shaft 1 10 by a taper lock bushing 436 which is in turn held against rotation relative the shaft 110 by a key 438. In a circumferential space defined by the stationary cam portion 430 and the adapter plate 432, an angular cam ring 440 is seated and it has a peripheral profile which is identical to that of the stationary cam portion 430. The cam ring 440 is dimensioned so that it is free to rotate about the axis of the cam shaft 110. The cam ring however can be held against rotation relative to the cam portion 430 by a spring biased pin 442 arranged to be received within any one of a plurality of circumferentially spaced holes 444 formed in the annular ring 440. To produce the maximum dwell the cam ring 440 is adjusted so that its profile is aligned with that of the cam 430. Increases in dwell time can be accomplished by manually withdrawing the pin from one of the holes in the cam 440 and rotating the cam ring to thereby extend the dwell period of the cam. According to the above construction it can be readily appreciated therefore that the seal bar drive of the present invention is also provided with the ability to adjust the push rod actuating cam to providea dwell period which holds the seal bar 340 in contact with the seal roll 106 for that period of time required to make a good quality weld.

AIR LOADED DRAW ROLLS In accordance with a further and equally important feature of the present invention the bag machine is provided with intermittently operating air loaded draw rolls for feeding the film to the seal bar. The upper draw roll is associated with fluid operated cylinders, either the hydraulic or pneumatic type, but herein preferably of the pneumatic type, which regulate the nip pressure between the rolls as required by the thickness of the film or whether gusseted or non-gusseted bags are being produced. It is apparent that when producing gusseted bags one edge of the film assumes a reverse fold resulting in four plys of film. Thus maintaining the feed rolls parallel would result in either too much nip pressure at the gusset, if a required nip pressure were to be maintained at the mouth of the bag, or no nip pressure at the mouth of the bag, if the nip pressure at the gusset were of a value required for positive film feeding. According, the upper feed roll of the present invention can be adjusted to assume a slightly non-parallel relation to the lower feed roll so that a substantially uniform nip pressure can be maintained along the width of the web when gusseted bags are being produced.

This feature of the present invention will be described in connection with the structure shown in FIGS. 12, 14 and 15. Referring first to FIGS. 14 and 15, the air loaded draw rolls, previously mentioned and indicated by the numeral 84, comprise an upper feed roll 446 extending transversely between the side frames 52. The ends of the draw roll 446 are mounted in bearings 448 (only one of which is shown in FIG. 15) secured in end blocks 450 pivotally connected to the side frames 52 by bolts 452 which are in effect pivot pins for the blocks 450. A lower draw roll 454 is mounted for rotation in the side frames 52 by bearings 456 and it has an extension 458 (on the right as viewed in FIG. 15) mounting a pulley 460 about which is trained a timing belt 462. A gear 464 fixed to the lower draw roll at a point adjacent the right side frame 52, as viewed in FIG. 15, meshes with an idler gear 465 which in turn meshes with a gear 466 keyed to the seal roll 106. This imparts rotation to the seal roll 106 in the same direction as the lower draw roll 454. Each of the draw rolls are provided with grooves 468 in which are disposed the upper and lower sets of stripper fingers 86 and 88 respectively. The upper set of stripper fingers 86 are individually bolted to the generally rectangular transversely extending support bar 90 having each end rigidly attached, by brackets 476, to the end blocks 450.

On the other hand the lower set of stripper fingers 88 are mounted on the support bar 91 which is rigidly secured by similar brackets 478 to the side frames 52.

At a point intermediate the bearings 448, carried by the end block 450, and the pivot bolt 452, laterally outwardly extending pins 480 are threaded into the end block 450 to extend through generally a crusiform opening 482 formed in each of the side frames 52 (FIG. 15). Cylinders 484, preferably pneumatic and of the single acting type wherein only the head end is supplied with pressure fluid, are mounted on the upper surface of the side frame 52 and are located so that a plane containing the axis of the cylinders 484 also contain the axis of the pins 480. Each of the cylinders have a projecting rod 490 which makes contact with the upper surface of the pins 480 while the diametrically opposed lower surface of the pins 480 are in contact with springs 492 disposed within one leg 494 of the crusiform opening 482. According to this construction it should be readily apparent that since the upper feed roll 446 is rotatably mounted in the end blocks 450 which in turn are pivotally connected to the side frames 52 by the bolts 452, the interaction of the cylinders 484 and the springs 492 can control the pressure between the draw rolls 446 and 454. Also, when desired, differential loading can be applied to the ends of the upper feed roll 446. It is to be understood that suitable controls, conventional in the art, are provided for regulating and controlling the supply of pressure fluid to the cylinders 484.

Operation of draw rolls is as follows. When a new roll of film is being threaded through the bag machine the conduits 486 are not supplied with pressure fluid thus rendering springs 492 operative to rotate the end blocks 450 in a counterclockwise direction as viewed in FIG. 14. This, of course, raises the upper feed roll 446 and the stripper fingers 86 which are also carried by the end block 450. This provides sufiicient space between the draw rolls 446 and 454 to facilitate threading the film therethrough Upon commencing normal machine operation the control circuit energizes valves which admit pressure fluid to the cylinders 484 by the conduits 486 extending the cylinder rods 490 which exert a downward force on the pins 480 overcoming in part the bias of the springs 492. Such action rotates the end blocks 450 about the pivot bolts 452 resulting in nip pressure between the feed rolls 446 and 454. The amount of nip pressure desired can obviously be regulated since the level of pressure of the actuating fluid supplied to the cylinders 484 can be easily regulated by the operator. As mentioned previously, in the event it is desired to equalize the nip pressure in such cases, for example, where gusseted bags are being produced, the value of pressure of the pressure fluid supplied to each of the cylinders 484 can be regulated to achieve this result and thereby constraining the upper feed roll 446 to assume a slight nonparallel relationship with the lower feed roll 454.

Whenever the machine is stopped the control system can be readily energized to connect the conduits 486 to exhaust venting the cylinders 484 to atmosphere. Under this condition the springs 492 exert an upward force on the pins 480 rotating the end blocks 450 in a counterclockwise direction (as viewed in FIG. 14) about the pivot bolts 452. Accordingly it will be seen that the draw rolls utilized in the bag machine of the present invention can be controlled to apply a selected nip pressure and could be readily released whenever the machine is stopped. Further by being able to comply different values of pressure to the cylinders 484 the nip pressure can be substantially equalized when producing gusseted bags.

SLOW DOWN AND D.C. DRIVE Also in accordance with the present invention means are provided for accurately adjusting the speed of the belt conveyor 112 to insure that the bag slow down mechanism momentarily grips the trailing edge of each bag before it is discharged to the stacking table 118. The particular means employed to produce the indicated result comprises course and fine adjustment potentiometers 496 and 500 respectively (FIG. 18). As a matter of convenience the potentiometer 496 is located at the main control panel of the machine which is approximately in the area of the seal mechanism 104. The fine adjustment potentiometer 500 is located within reach of the position the operator takes at the stacking table 118, either to observe the bags as a stack is being produced or to remove a completed stack of bags.

As shown in FIG. 18 the potentiometers 496 and 500 are electrically connected to the DC. motor which is connected to the line by a switch 502. The motor 140 has a pulley 504 keyed on its shaft. The belt 141 transfers the torque of the motor 140 to the double grooved pulley 142 mounted on the shaft 143 which also has keyed thereto the pulley 144 driving the belt 145 trained about the pulley 146 keyed to the shaft 147. The shaft 147, in addition, carries another pulley 514 driving a belt 516 trained about an idler pulley 518 and pulleys 520 and 522 keyed, respectively, to shafts 524 and 526 which mount the corrugating wheels 528.

The other groove of the pulley 142 engages a belt 530 trained about a pulley 532 which is keyed to a shaft 534 driving another shaft 536 by virtue of gears 538. Shaft 534 drives the upper belts 114 of the belt conveyor 112 while shaft 536 drives the lower belts 116. Due to the above described organization of structure it will be seen that the DC motor 140 provides the drive for the belt conveyor 112 and the corrugating rolls 134.

To adjust the speed of the motor 140 the fine adjustment potentiometer 500 is set to its mid position while the course adjustment potentiometer is adjusted to regulate the motor 140 so that the bags issuing from the corrugating rolls 134 are gripped by the slow down 136 in the vicinity of their trailing edge. Accurate adjustment of the index conveyor 112 is then accomplished by closely observing where contact with the bags is made by the slow down 136 and adjusting the potentiometer 500, from its previously set mid position, to change the speed of the motor 140 so that the bags are momentarily gripped at the trailing end before being discharged to the stacking table 1 18.

The remaining parts of the bag machine drive shown in FIG. 16 comprise a main motor 540 driving the shaft 110 through pulley 542, keyed on the motor shaft, and pulley 544, keyed on shaft 110, and having a belt 546 extending therebetween. Also keyed on the shaft 110 is a reduced diameter pulley 548 driving a belt 550, which in turn drives the shaft 132 by a pulley 554.

On the shaft 132 there is mounted the cam 128, for oscillating the idler shaft 122, through the linkages 124. The pulley 554 is provided with an additional belt groove in which is disposed a belt 556 for driving a shaft 558 by a pulley 560 supporting the lower bar of the slow down 136. As shown, the upper bar of the slow down 136 is driven by gears 562. To maintain proper tension of the belt 556 an idler tension pulley 563 is provided and it is mounted on a shaft 564.

Since the draw rolls 446 and 454 and the seal roll 106 are intermittently driven, the input torque to the pulley 460 is received through a shaft 566 mounting a clutch 568 and a brake 570. The belt 462 is trained on a pulley 572 mounted on the shaft 566. The degrees of rotation imparted to the shaft 566 is controlled by the development change device, generally indicated by the numeral 574, which determines the throw of the crank 322 and, of course, the angle through which the segment gear 326 oscillates.

In view of the above it should be apparent that the bag machine drive of the present invention provides a high degree of flexibility by independently controlling the bag belt conveyor to insure proper engagement of the bag by the slow down 136.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

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1. In a bag machine of the character described means, operable while the machine is operating for increasing or decreasing the distance a thermoplastic web is indexed to thereby produce bags of a desired width, said means comprising a drive arrangement including a connecting rod having one end rotatably mounted on a pin rotatable about or alignable with the axis of an input shaft and the other end rotatably mounted on a pin fixed to a sector gear, means for adjusting the first mentioned of said pins relative to the axis of such input shaft, said adjusting means including a screw actuated translatable block, said screw provided with a metal cog wheel, and manually actuated means locatable in the orbit of said cog wheel for incrementally rotating said screw and thus moving the first mentioned of said pins relative to the axis of the input shaft, said manually actuated means carrying plastic blocks for establishing engagement with said cog wheel.
 2. An apparatus for producing bags from thermoplastic sheet material comprising means for intermittently feeding the material; means, including a heated seal bar, for transversely sealing and cutting the material when the material is momentarily at rest; means, coordinated with the intermittent feeding of the material, for actuating said seal bar toward and away from the material; and means for displacing said seal bar to render it ineffective to make contact with the material when intermittent feeding thereof is interrupted while said actuation of the seal bar continues.
 3. The apparatus according to claim 2 wherein said last mentioned means is operable to render said seal bar effective to engage the material when intermittent feeding of the material is commenced.
 4. The apparatus according to claim 2 wherein said seal bar actuating means comprises reciprocating drive members; a beam carrying the seal bar; means, engageable with the end of said beam; for slidably receiving respective end portions of said drive members; and fluid actuators rigidly connected to said drive members for moving said means slidably receiving the drive members away from the sheet material.
 5. The apparatus according to claim 2 wherein said last mentioned means is operable to displace said seal bar when the bag producing apparatus is inactive or inactivated for more than one bag making cycle.
 6. A bag machine including a bar for severing and sealing thermoplastic web material, said bar being heated and cooperable with a web supporting member to effect such severing and sealing when said bar establishes momentary pressure engagement with said supporting member, the improvement in said seal bar comprising a beam, each end of said beam slidably receiving reciprocable rods, the ends of said rods being engageable with abutment surfaces of said beam, and means rigidly mounted on said rods being operable to establish forceable engagement between the upper ends of said rods and said abutment surfaces preventing relative movement therebetween during normal operation or to slide said beam axially relative to said rods when bag machine operation is interrupted.
 7. The apparatus according to claim 6 wherein said abutments are adjustable axially relative to said rods for adjusting the force applied by said bar to said web supporting member.
 8. The apparatus according to claim 7 wherein means, associated with said abutment surfaces, are provided for indicating their adjusted positioN. 